To meet federal requirements, a levee reconstruction project for the Indianapolis Southport Advanced Wastewater Treatment (AWT) plant planned along Little Buck Creek was one of the largest combined sewer overflow projects for the city of Indianapolis and part of the more extensive Deep Rock Tunnel Connector project.
Significant toe erosion on the north side of the levee embankment resulted from flood events and high water flow from the adjacent creek. Little Buck Creek flows as low as 1-ft deep with velocities of 3 ft per second to as much as 8 ft per second with a depth of 12 to 15 ft during a flooding event. Mitigation was required to prevent future erosion caused by the creek’s varying depths and flows.
A wall system with native vegetation and enough sustainability to control erosion from the creek was preferred along the levee. The chosen vegetated gravity wall system, Geoweb, pre- served the levee elevation by opening up the creek’s water capacity. The wall structure also protected the Southport AWT plant and wastewater processing pond from a 500- year flood event. The wall face area was 12,000 sq ft, its length was 1,500 ft, and its height was 5 to 12 ft.
The vegetated retaining wall system reduced environ- mental impacts, protected the reconstructed levee from scour and erosion, and satisfied regulatory requirements. Since installation in late 2012, the levee wall has performed well during several rain events.